Talk:Daylight saving time

The title figure is wrong. DST starts at 2am, and ends at 2am. See

https://www.nist.gov/pml/time-and-frequency-division/popular-links/daylight-saving-time-dst Betaneptune (talk) 14:20, 27 September 2025 (UTC)

The last line in the caption: "Specific times of the clock change vary by jurisdiction". The diagram is not intended to illustrate the US rules specially, it just illustrates the one-hour jump and its direction. The world is a very big place, and the United States is just one part of it. Indefatigable (talk) 18:11, 27 September 2025 (UTC)

But the US is the source of time for the world. NIST in particular. So it seems to me that the figure should be based on the US times, not the times of some random place, which it is now. Also, Wikipedia is based in the US. Maybe the figure should be omitted altogether. As is, the last line in the caption looks like the fine print that no one reads. Maybe add a couple of clocks for the UK method to illustrate that different regions change at different times. The UK changes from 1 to 2 for British Summer Time, and from 2 to 1 for Standard Time. Different from the US times!

"Through its own time scale, NIST provides time to the nation and the world via the internet and radio."

Quote is from https://www.nist.gov/time-frequency Retrieved 2025-09-27 Betaneptune (talk) 20:46, 27 September 2025 (UTC)

All the quote from NIST means that they didn't block phone calls or internet connections from outside the US. There are a variety of national time laboratories that cooperate, through the International Earth Rotation and Reference Systems Service. Jc3s5h (talk) 21:07, 27 September 2025 (UTC)

It clearly says that "NIST provides time to the nation and the world". Do you see the word "provides" there? Yes, there are atomic clocks -- weighted, mind you -- around the world. Something like 400, I believe. Now, we can't have 400 different independent sources of time! So NIST calculates them and comes up with a single time source. It says "NIST provides". That's more than not blocking phone calls and internet connections. In fact, what does that have to do with this anyway, especially phone calls? Betaneptune (talk) 21:16, 27 September 2025 (UTC)

Do you see the word "provides" there? Yes, I see the word "provides", which does NOT necessarily mean "is the authoritative source of". The full paragraph from which that quote was extracted is

NIST, in coordination with the U.S. Naval Observatory, provides official time for the United States. NIST builds and operates the country’s most accurate atomic clocks, which help set the global time scale known as Coordinated Universal Time. Through its own time scale, NIST provides time to the nation and the world via the internet and radio. NIST develops chip-scale atomic clocks and calibrates clocks for customers such as stock exchanges. NIST researchers are working with international colleagues to redefine the second — the fundamental unit of time — using next-generation optical clocks.

That only uses "official" when referring to the US. It does not state that they provide official time to any other country, just that if you want to get UTC, you can get it from NIST. The National Physical Laboratory (NPL) in the UK, for example, also provides time services, and they say

NPL operates the national time scale UTC(NPL) and the UK primary frequency standards, and uses these to contribute to global timekeeping. We also disseminate accurate time and frequency to users across the UK, via services such as the MSF radio time signal, our internet time service, and NPLTime®. Atomic timekeeping underpins technologies that are part of our daily lives, such as mobile phones, the internet and global navigation satellite systems.

so they are the providers of official time in the UK. Users outside the UK can also use their time and frequency services - for example, I was able to use the SNTP command-line client on my machine to ping one of their NTP servers. A radio that can receive signals from their radio time signal, and that is located outside the UK, could also get time from them. as their page on that signal says ("The MSF radio signal is a dedicated standard-frequency and time broadcast that provides an accurate and reliable source of UK civil time. It is available 24 hours a day across the whole of the UK and beyond. ... The signal covers the whole of the UK, and can also be received throughout most of northern and western Europe.")

Yes, there are atomic clocks -- weighted, mind you -- around the world. Something like 400, I believe. Now, we can't have 400 different independent sources of time! So NIST calculates them and comes up with a single time source. You're talking there about International Atomic Time (TAI). That article says:

TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories worldwide.^[1] The majority of the clocks involved are caesium clocks; the International System of Units (SI) definition of the second is based on caesium. The clocks are compared using GPS signals and two-way satellite time and frequency transfer.^[2] Due to the signal averaging TAI is an order of magnitude more stable than its best constituent clock.

The participating institutions each broadcast, in real time, a frequency signal with timecodes, which is their estimate of TAI. Time codes are usually published in the form of UTC, which differs from TAI by a well-known integer number of seconds. These time scales are denoted in the form UTC(NPL) in the UTC form, where NPL here identifies the National Physical Laboratory, UK. The TAI form may be denoted TAI(NPL). The latter is not to be confused with TA(NPL), which denotes an independent atomic time scale, not synchronised to TAI or to anything else.

The clocks at different institutions are regularly compared against each other. The International Bureau of Weights and Measures (BIPM, France), combines these measurements to retrospectively calculate the weighted average that forms the most stable time scale possible.^[1] This combined time scale is published monthly in "Circular T",^[3] and is the canonical TAI. This time scale is expressed in the form of tables of differences UTC − UTC(k) (equal to TAI − TAI(k)) for each participating institution k. The same circular also gives tables of TAI − TA(k), for the various unsynchronised atomic time scales.

So, no, NIST does NOT "[calculate] them and [come] up with a single time source." That's done by the BIPM, who publish Circular T, containing tables of differences between their official UTC/TAI and the estimates of UTC/TAI provided by various laboratories, including but not limited to the NIST. What NIST provides is UTC(NIST), just as the NPL provides UTC(NPL). To convert those to UTC, the correction from the most recent Circular T for that particular source would be applied.

It says "NIST provides". That's more than not blocking phone calls and internet connections. Yes, it's providing unblocked radio, telephone, and Internet time services.

In fact, what does that have to do with this anyway, especially phone calls? Both NIST and NPL, and possibly other national time services, provide dial-up time services. The NIST's dial-up time service does not indicate that it is unavailable outside the US. The NPL's dial-up time service is not available outside the UK ("No, British Telecom’s premium rate telephone numbers, including that used by the NPL TTS, cannot be called from outside the UK.") Guy Harris (talk) 22:44, 27 September 2025 (UTC)

You wrote, :That only uses "official" when referring to the US. It does not state that they provide official time to any other country,"

NIST wrote, "Through its own time scale, NIST provides time to the nation and the world via the internet and radio."

It says the nation AND THE 'WORLD'. Why should NIST provide unofficial time to the world? The article also doesn't specify which galaxy is being assumed. And all sorts of things. IOW, you're nitpicking and being, uh, overly pedantic.

Betaneptune (talk) 23:29, 27 September 2025 (UTC)

Why should NIST provide unofficial time to the world? Because it'd be more effort to prevent anybody outside the US from communicating with their NTP server?

"Official" time, for a nation, is determined by the national government; the US government has designated the NIST as the provider of official time in the US - as their website says, "NIST, in coordination with the U.S. Naval Observatory, provides official time for the United States." The UK government has designated the NTP, not the NIST, as the provider of official time in the UK.

IOW You misspelled "IMO". Guy Harris (talk) 23:51, 27 September 2025 (UTC)

International Earth Rotation and Reference Systems Service calculates a consensus time scale and a list of how much each national time scale is off from the consensus. National time laboratories steer their clock ensemble toward the consensus. To confirm this read a book such as McCarthy & Seidelmann, Time From Earth Rotation to Atomic Physics (Wiley-VCH, 2009). Jc3s5h (talk) 22:44, 27 September 2025 (UTC)

Fine. Leave it as it is. Fine, keep your misleading figure. Yes, there's a complex web of places involved, but "provides" overrides all that.

"International Earth Rotation and Reference Systems Service" Yes, I saw that article. Seems to me, it had more to do with polar motion of the earth. Fine, keep your, uh, diagrams.

Wikipedia is an American invention, located in the US, using American English, AFAICT.

I had an even worse time with the "planetary system" and "2001" talk pages. I gave perfectly reasonable things to change and got shot down every time. I gave perfectly reasonable and correct points and got shot down every time. One person claimed I was a troll. In another case I was told "Original research", even though other things in the article were also original research. Apparently it's only "original research" when I mention it. I was talking about obvious things in the movie. You don't need some stupid reference for it! So be it. No more donations for you! I used to donate, but not anymore. Betaneptune (talk) 23:21, 27 September 2025 (UTC)

but "provides" overrides all that. False, as explained repeatedly.

"International Earth Rotation and Reference Systems Service" Yes, I saw that article. Seems to me, it had more to do with polar motion of the earth. He may have mistakenly referred to the International Earth Rotation and Reference Systems Service, which deals with the "leap seconds" part of UTC, rather than the International Bureau of Weights and Measures (BIPM), which deals with the "Coordinated" part of UTC. The BIPM are the ones who do the work to coordinate all the individual atomic clocks to generate an averaged time value.

Wikipedia is an American invention Wikipedia was initially founded by some US citizens, and the Wikimedia Foundation is a US foundation headquartered in the US...

located in the US ...and its first server was in the US, with the application servers all currently in the US and several caching servers both inside and outside the US...

using American English ...but with the English-language Wikipedia supporting articles in American English and Australian English and British English and Canadian English and ... and Hiberno-English and ... and Indian English ... and New Zealand English ... and... (see the "See also" for the full set of templates for various English variants), so, no, it's not solely "using American English". (There are also non-English Wikipedias, but this article is in the English-language Wikipedia.)

But none of that makes the US primus inter pares in the English-language Wikipedia. Guy Harris (talk) 06:35, 28 September 2025 (UTC)

I agree, but it might be nice to have an illustration that matches some large jurisdiction, rather than none at all. Jc3s5h (talk) 18:19, 27 September 2025 (UTC)

the map of North America incorrectly features British Colombia as using daylight savings time. Gosensgo1992 (talk) 03:00, 7 March 2026 (UTC)

BC has switched to DST ("summer time") every year since the 1950s. The map is not about being on "permanent" DST, but rather using it alternately each year with Pacific Standard Time (PST). Zefr (talk) 04:51, 7 March 2026 (UTC)

yes but I was wondering about their upcoming permanent change Gosensgo1992 (talk) 04:59, 7 March 2026 (UTC)

thank you for replying:) Gosensgo1992 (talk) 04:59, 7 March 2026 (UTC)

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